Production of alkylaromatic compounds

ABSTRACT

A process for producing a monoalkylation aromatic product, such as ethylbenzene and cumene, utilizing an alkylation reactor zone and a transalkylation zone in series or a combined alkylation and transkylation reactor zone.

[0001] The present invention relates generally to improvements in theproduction of alkyl aromatic compounds, particularly cumene andethylbenzene, utilizing alkylation and transalkylation in novel seriesor combination configurations to achieve significant improvements inprocess efficiencies.

BACKGROUND OF THE INVENTION

[0002] Cumene and Cumene Production

[0003] Cumene is an aromatic compound. It is a clear liquid at ambientconditions. High purity cumene is conventionally manufactured frompropylene and benzene. Cumene is used today primarily as a feed inmanufacturing the products phenol and acetone, which are two importantpetrochemicals with many uses in the chemical and polymer industries.Global cumene production in 1998 was about 7 million metric tons.

[0004] Cumene was first synthesized in large quantities during World WarII as an aviation gasoline. It has a high heating value and a highoctane number, but it is not economically competitive today as a fuel.Its presence in gasoline is now incidental, being an inevitable minorreaction product of refinery processes such as catalytic reforming andsteam cracking.

[0005] Production of cumene was considered a rather conventional androutine business for many years, but recently has generated considerableexcitement for two reasons. First, the demand for phenol formanufacturing polycarbonates is accelerating rapidly owing to thebroadening applications of polycarbonates in the electronic, healthcare,and automobile industries. Second, successful development andcommercialization of the zeolite-based alkylation technology for theisopropylation of benzene to cumene has rendered obsolete the olderprocesses which were based on solid phosphoric acid and aluminumchloride. Within a period of just over two years during 1996-98, overone half of the cumene capacity in the world was converted to the newzeolite technologies.

[0006] New zeolite-based cumene technologies developed by Mobil/Badger,Dow/Kellogg, and UOP carry out the alkylation of benzene and propylenein liquid phase in the presence of a solid acidic zeolite catalyst. Aprocess developed by CDTech achieves the alkylation of benzene andpropylene in mixed phases in a catalytic distillation column packed withboth distillation devices and bales of zeolite catalysts. FIG. 1 is asimplified representation of the zeolite-based cumene technologies. Allof these zeolite-based cumene technologies utilize a separatetransalkylation zone which is operated in parallel with the alkylationzone, to react a mixture of benzene and the polyisopropylbenzenealkylation byproducts to form additional cumene in liquid phase in thepresence of a solid acidic catalyst. A separation zone is utilized torecover the unreacted benzene and polyisopropylbenzenes for recycle, andto isolate the desired cumene product.

[0007] Ethylbenzene and Ethylbenzene Production

[0008] Ethylbenzene is a commodity chemical currently used mostly forthe production of styrene. Global ethylbenzene production in 1998 wasabout 19 million metric tons. Ethyl-benzene may be prepared by a numberof different chemical processes, but present commercial ethylbenzeneproduction is dominated by zeolite-based technologies. The firstzeolite-based ethylbenzene process, developed jointly by Mobil andBadger in the early 1980s, utilizes a combination of vapor phasealkylation of benzene with ethylene and vapor phase transalkylation of abenzene and polyethylbenzene mixture. Both the alkylation andtransalkylation steps are carried out in the presence of solid acidicZSM-5 catalysts.

[0009] Several liquid-phase zeolite-based ethylbenzene technologies weredeveloped in the late 1980s and in the 1990s by UOP/Lummus andMobil/Badger. Alkylation of benzene with ethylene and transalkylation ofmixtures of benzene and polyethylbenzenes are carried out in liquidphase in the presence of solid acidic zeolite catalysts. Catalysts thatcan be used for alkylation of benzene with ethylene and fortransalkylation of benzene and polyethylbenzenes in at least partialliquid phase include zeolite beta, zeolite Y, ZSM-5, PSH-3, ITQ-2,ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, faujasite,mordenite, porous crystalline magnesium silicates, and tungstatemodified zirconia.

[0010] Processes for the production of ethylbenzene overintermediate-pore size zeolites are described in U.S. Pat. No. 3,751,504(Keown), U.S. Pat. No. 4,547,605 (Kresge), and U.S. Pat. No. 4,016,218(Haag). U.S. Pat. No. 4,169,111 (Wight) and U.S. Pat. No. 4,459,426(Inwood) disclose production of ethylbenzene over large-pore sizezeolites such as zeolite Y. A process for ethylbenzene production overzeolite ZSM-12 is described in U.S. Pat. No. 3,755,483 (Burress). Liquidphase synthesis of ethylbenzene with zeolite beta is described in U.S.Pat. No. 4,891,458.

[0011] To minimize the formation of polyalkylaromatics and otherundesired impurities (e.g., oligomers of the olefin), production ofalkylaromatics such as ethylbenzene and cumene typically operates withrelatively high (excess) mole ratios of aromatic (e.g., benzene) toolefin (e.g., ethylene or propylene) in the alkylation reactor feed.Zeolite-based alkylaromatic processes generally operate at aromatic toolefin feed molar ratios of three or above, while aluminumchloride-based processes often operate at aromatic to olefin molarratios of three and below. In both cases, however, thepolyalkylaromatics are produced at sufficiently high levels that itwould be prohibitively expensive to simply dispose f them as low valuebyproducts. Instead, these polyalkylated aromatics are typically reactedfurther with feed aromatic to form additional monoalkylate viatransalkylation reactions.

[0012] In the case of the Mobil/Badger vapor phase ethylbenzene processmentioned above, the transalkylation reaction may take place in thealkylation reactor or in a separate transalkylation reactor. U.S. Pat.No. 5,902,917 (Collins) and U.S. Pat. No. 6,096,935 (Schulz) describeprocesses for the production of alkylaromatics wherein a feedstock isfirst fed to a transalkylation zone and the entire effluent from thetransalkylation zone is then cascaded directly into an alkylation zonealong with an olefin alkylating agent.

[0013] Conventionally, relatively high molar ratios of aromatic (e.g.,benzene) to olefin (e.g., ethylene or propylene) have been usedsuccessfully commercially in the production of alkylaromatics (e.g.,ethylbenzene or cumene) to minimize the formation of polyalkylaromaticsand other undesired impurities (e.g., oligomers of the olefins). Thedisadvantage of using high molar ratios of aromatic to olefin, however,is that the recovery and the subsequent circulation (re-use) of theunreacted aromatics consumes very substantial amounts of energy whichincreases the production cost of the desired alkylaromatics.

[0014] The recovery and circulation of large amounts of unreactedaromatics also requires larger capacity separation equipment (usuallydistillation columns) and larger pumps, both of which increase capitalcost of the plant, and thus also increase the cost of production.

[0015] It is therefore of crucial interest to minimize the amount ofexcess aromatics that is used and needs to be recovered and subsequentlycirculated in order to minimize the production cost. It is of even moreimportance today in the production of highly competitive commoditychemicals (e.g., ethylbenzene and cumene) which are produced and tradedglobally, and at a time when the energy costs are high. Low aromaticscirculation results in lower energy consumption, lower capitalinvestment and thus a more efficient plant. This in turn enables aproducer to establish itself as a low cost producer in a favorable(competitive) marketing position.

[0016] Because of these disadvantages and limitations of the prior artprocesses, it is desired to provide improved processes and apparatus forthe production of alkylaromatic compounds. In this invention, tworeaction configurations are provided which have been found tosignificantly reduce the total aromatic circulation, compared with priorart processes, at all aromatic to olefin ratios.

OBJECTS OF THE INVENTION

[0017] Accordingly, a general object of this invention is to provideimproved processes and apparatus for the production of alkylaromaticcompounds, particularly cumene and ethylbenzene.

[0018] More specifically, it is a principal object of this invention toprovide processes and apparatus for the production of alkylaromaticcompounds using less circulation of aromatics than in conventionalprocesses.

[0019] It is a further principal object of this invention to provideprocesses and apparatus for the production of alkylaromatic compoundswhich use relatively low circulation of aromatics without increasing theproduction of unwanted byproducts, specifically polyalkylaromatics.

[0020] A specific object of this invention is to provide processes andapparatus for the production of alkylaromatic compounds which utilize incombination a reaction zone or step, broadly comprising alkylation andtransalkylation, together with a separation zone or step.

[0021] Another specific object of this invention is to provide areaction zone for the production of alkylaromatic compounds comprisingan alkylation unit and a transalkylation unit in a particular seriesconfiguration.

[0022] Still another specific object of this invention is to provide areaction zone for the production of alkylaromatic compounds comprising acombined alkylation-transalkylation unit.

[0023] Yet a further specific object of this invention is to preparealkylaromatic compounds, such as cumene and ethylbenzene, utilizing theprocesses and apparatus described herein.

[0024] Other objects and advantages of the present invention will inpart be obvious and will in part appear hereinafter. The inventionaccordingly comprises, but is not limited to, the processes and relatedapparatus, involving the several steps and the various components, andthe relation and order of one or more such steps and components withrespect to each of the others, as exemplified by the followingdescription and the accompanying drawings. Various modifications of andvariations on the processes and apparatus as herein described will beapparent to those skilled in the art, and all such modifications andvariations are considered within the scope of the invention.

SUMMARY OF THE INVENTION

[0025] The present invention relates generally to improvements inalkylation and transalkylation processes and apparatus in the productionof alkylaromatic compounds, for example cumene and ethylbenzene,utilizing a reaction section and a separation section. In accordancewith the present invention, two novel alternative reactor configurationsare provided for the reaction section. The two reaction sectionconfigurations provided in this invention share certain importantcommonalities including that both of these novel configurations requiresignificantly less total aromatics distillation and circulation(recycle) than do the conventional configurations of both parallelalkylation/transalkylation reactors and the transalkylator-alkylatorcascaded configuration described in U.S. Pat. No. 5,902,917 (Collins)and U.S. Pat. No. 6,096,935 (Schulz), even when operated at the samealkylator feed aromatics to olefin molar ratio, thereby reducing thecapital and utility costs of producing the desired alkylaromatics.

[0026] In a first embodiment of the improved alkylaromatic productionprocesses and apparatus according to this invention, the reactionsection comprises an alkylation zone and a transalkylation zoneconfigured to operate in a novel series arrangement. In this firstembodiment, two or more separate feeds respectively consistingessentially of fresh and recycle aromatics and fresh olefin, or one ormore at least partially combined feeds of aromatics and/or olefin, aresent to an alkylation zone where the aromatics and olefin are reacted inthe presence of an alkylation catalyst in the alkylation zone. Theeffluent from the alkylation zone is sent to a transalkylation zonetogether with recycled polyalkylaromatics for the production ofadditional alkylaromatics. The alkylation and the transalkylation zonescan be housed in the same vessel or in different vessels.

[0027] The alkylation is carried out substantially adiabatically in atleast partial liquid phase, at temperatures between about 150° F. (66°C.) and 900° F. (482° C.) and at pressures between about 150 psig (1034kPAg) and 2000 psig (13788 kPAg), over one or more beds of suitablealkylation catalyst(s) consisting essentially of at least one solid acidoxide selected from the group consisting of: zeolite beta, zeolite Y,ZSM-5, PSH-3, ITQ-2, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58,MCM-68, faujasite, mordenite, porous crystalline magnesium silicates,and tungstate modified zirconia. The overall molar ratio of aromatics toolefin fed to the alkylation zone is between about 1:1 and 20:1. Theolefin fed to the alkylation zone is essentially completely reacted withthe aromatics feed. The alkylation zone can be housed in one or morevessels.

[0028] The transalkylation is carried out substantially adiabatically inat least partial liquid phase, at temperatures between about 150° F.(66° C.) and 900° F. (482° C.) and at pressures between about 150 psig(1034 kPAg) and 2000 psig (13788 kPAg), over one or more beds ofsuitable transalkylation catalyst(s) consisting essentially of at leastone solid acid oxide selected from the group consisting of: zeolitebeta, zeolite Y, ZSM-5, PSH-3, ITQ-2, ZSM-12, MCM-22, MCM-36, MCM-49,MCM-56, MCM-58, MCM-68, faujasite, mordenite, porous crystallinemagnesium silicates, and tungstate modified zirconia. The overall weightratio of aromatics to polyaromatics fed to the transalkylation zone isbetween about 0.2:1 and 20:1. The transalkylation zone can be housedeither in one or more separate vessels or, alternatively, in the samevessel or vessels where the alkylation zone is housed.

[0029] This process and apparatus may further comprise a separation zonewherein unreacted aromatic and polyalkylaromatic compounds are recoveredand recycled, and the desired alkylaromatic product, for example cumeneor ethylbenzene, is isolated.

[0030] In a second embodiment of the improved alkylaromatic productionprocesses and apparatus according to this invention, the reactionsection comprises a novel combined alkylation-transalkylation zone. Inthis second embodiment, three or more separate feeds respectivelyconsisting essentially of fresh and recycle aromatics, fresh olefin, andrecycled polyalkylaromatics, or one or more at least partially combinedfeeds of aromatics, olefin, and/or polyalkylaromatics, are sent to acombined alkylation-transalkylation zone where the components arereacted in the presence of catalyst. The effluent from the combinedreaction zone is sent to a separation zone where unreacted aromatics andpolyalkylaromatics are recovered and recycled, and the desiredalkylaromatic product, for example cumene or ethylbenzene, is isolated.

[0031] The reaction is carried out substantially adiabatically in atleast partial liquid phase, at temperatures between about 150° F. (66°C.) and 900° F. (482° C.) and at pressures between about 150 (1034 kPAg)and 2000 psig (13788 kPAg), over one or more beds of suitablealkylation-transalkylation catalyst(s) comprising at least one solidacid oxide selected from the group consisting of: zeolite beta, zeoliteY, ZSM-5, PSH-3, ITQ-2, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58,MCM-68, faujasite, mordenite, porous crystalline magnesium silicates,and tungstate modified zirconia. In this environment, it has been foundthat the reaction of aromatics and olefin to produce themonoalkylaromatics and polyalkylaromatics, and the reaction of aromaticsand polyalkylaromatics to produce additional monoalkylaromatics, takeplace simultaneously over at least one catalyst bed.

[0032] The combined alkylation-transalkylation reaction zone can behoused in one or more vessels. The overall molar ratio of aromatics toolefin fed to the combined reaction zone is between about 1:1 and 20:1.The olefin fed to the combined reaction zone is essentially completelyreacted. The overall weight ratio of aromatics to polyalkylaromatics fedto the combined reaction zone is between about 0.2:1 and 20:1.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a schematic representation of a first prior art process,as discussed above, for the production of alkylaromatic compounds inwhich separate alkylation and transalkylation reactors are configured ina conventional parallel mode.

[0034]FIG. 2 is a schematic representation of a second prior artprocess, as discussed above, for the production of alkylaromaticcompounds, a cascaded configuration in which the entire effluent fromthe transalkylation zone is cascaded directly into an alkylation zonealong with an olefin.

[0035]FIG. 3 is a schematic representation of a first embodiment of thepresent invention wherein the reaction section comprises an alkylationzone and a transalkylation zone configured to operate in series.

[0036]FIG. 4 is a schematic representation of a second embodiment of thepresent invention wherein the reaction section comprises a combinedalkylation-transalkylation zone.

[0037]FIG. 5 is a graph comparing total benzene circulation forproduction of cumene at varying alkylator benzene/propylene feed ratiosfor the prior art reactor configurations of FIGS. 1 and 2 with those forthe reactor configurations of the present invention, namely FIGS. 3 and4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0038] The novelty of the present invention can best be understood bycomparison with and contrast to two important prior art approaches toproducing alkylaromatic compounds.

[0039] A first familiar conventional approach to the production ofalkylaromatic compounds, wherein separate alkylation and transalkylationreactors are used and operated in parallel mode, is illustratedschematically in FIG. 1. As shown in FIG. 1, the fresh aromatics feedcan enter the process via line 100 to the separation zone 120, via line101 into the alkylation zone 140, or via line 102 into thetransalkylation zone 130. Part of the aromatic feed recovered from theseparation zone 120 is sent to the alkylation zone 140 via line 105. Asecond part of the aromatic feed recovered in the separation zone 120 issent to the transalkylation zone 130 via line 106. Fresh olefin feed isintroduced into the alkylation zone 140 via line 103, and the effluentfrom the alkylation zone 140 is sent to the separation zone 120 via line107. The polyalkylaromatics product recovered in the separation zone 120is sent to the transalkylator 130 via line 108. The effluent from thetransalkylation zone 130 is sent to the separation zone 120 via line109.

[0040] A second familiar conventional approach to the production ofalkylaromatic compounds, utilizing a cascaded process as described inU.S. Pat. No. 5,902,917 (Collins) and U.S. Pat. No. 6,096,935 (Schulz),is illustrated schematically in FIG. 2. As shown in FIG. 2, the fresharomatics feed can enter the process either via line 200 to theseparation zone 220, via line 201 to the transalkylation zone 230, orvia line 202 into the alkylation zone 240. A first part of the aromaticfeed recovered from the separation zone 220 is sent to thetransalkylation zone 230 via line 203. A second part of the aromaticfeed recovered from the separation section 220 is introduced into thealkylation zone 240 via line 206. The polyalkylaromatic productrecovered from the separation zone 220 is sent to the transalkylationzone 230 via line 204. The effluent from the transalkylation zone 230 issent to the alkylation zone 240 via line 205. The fresh olefin feed tothe process is introduced into the alkylation zone 240 via line 207whereas the effluent from the alkylation zone 240 is sent to theseparation zone 220 via line 208.

[0041] In contrast to the prior art configurations, a first embodimentof the present invention wherein the reaction section comprises analkylation zone and a transalkylation zone configured to operate inseries is illustrated schematically in FIG. 3. As shown in FIG. 3, thefresh aromatics feed 300 can enter the process either via line 301 intoseparation zone 320, via line 302 into the alkylation zone 340 or,alternatively, via line 305 into the transalkylation zone 330. Thearomatic product recovered from separation zone 320 is introduced intothe alkylation zone 340 via line 303, and the fresh olefin feed entersthe process via line 304 into the alkylation zone 340. The effluent fromthe alkylation zone 340 is sent to the transalkylation zone 330 via line306. The polyalkylaromatic product recovered in separation zone 320 isintroduced into the transalkylation zone 330 via line 307. The effluentfrom the transalkylation zone 330 is sent to separation zone 320 vialine 308. The monoalkylated product is removed from the separation zone320 via line 321.

[0042] As seen in FIG. 3, the first embodiment of the present inventioncomprises the following process steps:

[0043] (a) introducing into an alkylation zone by two or more individualcomponent feeds or one or more at least partly combined feeds, areaction mixture comprising fresh and recycle aromatics and fresholefin, wherein the molar ratio of aromatics to olefin in the mixture isin excess of 1:1, and also wherein the alkylation zone includes asuitable alkylation catalyst(s);

[0044] (b) contacting the aromatic/olefin mixture with the alkylationcatalyst(s) under sufficient alkylation conditions to react essentiallyall the olefins in the mixture to monoalkylated aromatics andpolyalkylated aromatics, to produce an effluent from the alkylation zonecomprising monoalkylated and polyalkylated aromatics and the unreactedaromatics;

[0045] (c) introducing a feed into a transalkylation zone, the feedcomprising the effluent from the alkylation zone, recycledpolyalkylaromatics, and possibly additional aromatics, wherein thetransalkylation zone includes a suitable transalkylation catalyst;

[0046] (d) contacting the feed to the transalkylation zone with thetransalkylation catalyst under sufficient transalkylation conditions toreact at least a part of the aromatics and the polyalkylated aromaticsin the feed to additional monoalkylated aromatics to produce an effluentfrom the transalkylation zone comprising the desired mono-alkylatedaromatics and the unreacted aromatics and polyalkylated aromatics; and,

[0047] (e) introducing the transalkylation zone effluent into aseparation zone wherein the desired monoalkylated aromatics product isisolated and recovered and the unreacted aromatics and polyalkylatedaromatics are recovered and recycled.

[0048] The alkylation step of this first embodiment of the presentinvention may be carried out in at least partial liquid phase attemperatures between about 150° F. (66° C.) and 900° F. (482° C.) and atpressures between about 150 psig (1034 kPAg) and 2000 psig (13788 kPAg),over one or more beds of suitable alkylation catalyst(s) comprising atleast one solid acid oxide selected from the group consisting of:zeolite beta, zeolite Y, ZSM-5, PSH-3, ITQ-2, ZSM-12, MCM-22, MCM-36,MCM-49, MCM-56, MCM-58, MCM-68, faujasite, mordenite, porous crystallinemagnesium silicates, and tungstate modified zirconia. The overall molarratio of aromatics to olefin fed to the alkylation zone may be betweenabout 1:1 to 20:1. The olefin fed to the alkylation zone is essentiallycompletely reacted with the aromatics feed. The alkylation zone can behoused in one or more vessels. Each alkylation vessel can have one ormore catalyst beds containing the same or different alkylation catalystsor catalyst mixtures. Part of the total effluent from the alkylationzone may be recycled back to some or all of the alkylation catalystbeds, with or without cooling, for temperature control purposes.

[0049] Zeolite beta catalyst is described in U.S. Pat. No. 3,308,069 andRe. 28,341. Different versions of zeolite Y are described in U.S. Pat.Nos. 3,130,007; 3,293,192; 3,449,070; and 3,442,795. ZSM-5 is describedin detail in U.S. Pat. No. 3,702,886, and Re. 29,948. ZSM-12 isdescribed in U.S. Pat. No. 3,832,449. PSH-3 is disclosed in U.S. Pat.No. 4,439,409. ITQ-2 is disclosed in U.S. Pat. No. 6,231,751.

[0050] MCM-22 catalyst and its use to catalyze the synthesis ofalkylaromatics are described in U.S. Pat. Nos. 4,954,325; 4,992,606;5,077,445; and 5,334,795. MCM-36 and its use in the synthesis ofalkylaromatics are described in U.S. Pat. Nos. 5,250,277; 5,292,698; and5,258,565. MCM-49 and its use in the synthesis of alkylaromatics aredescribed in U.S. Pat. Nos. 5,236,575; 5,493,065; and 5,371,310. MCM-56and its use to catalyze the synthesis of alkylaromatics are described inU.S. Pat. Nos. 5,362,697; 5,453,554; 5,557,024; and 6,051,521. MCM-58and its use for the production of alkylaromatics are described in U.S.Pat. Nos. 5,437,855 and 5,569,805. MCM-68 and its use for the productionof alkylaromatics are described in U.S. Pat. No. 6,049,018. The use oftungstate modified zirconia to catalyze the synthesis of alkylaromaticsis described in U.S. Pat. No. 5,563,311.

[0051] The transalkylation step of this first embodiment of the presentinvention is carried out in at least partial liquid phase attemperatures between about 150° and 900° F. and at pressures betweenabout 150 and 2000 psig, over one or more beds of transalkylationcatalyst(s) comprising at least one solid acid oxide selected from thegroup consisting of: zeolite beta, zeolite Y, ZSM-5, PSH-3, ITQ-2,ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, faujasite,mordenite, porous crystalline magnesium silicates, and tungstatemodified zirconia. The overall weight ratio of aromatics topolyalkylaromatics fed to the transalkylation zone may be between about0.2:1 and 20:1. The transalkylation zone can be housed either in one ormore separate vessels or, alternatively, in the same vessel or vesselswhere the alkylation zone is housed. The transalkylation zone can haveone or more catalyst beds containing the same or differenttransalkylation catalysts or catalyst mixtures.

[0052] A second embodiment of the present invention wherein the reactionsection comprises a combined alkylation-transalkylation zone isillustrated schematically in FIG. 4. As shown in FIG. 4, the fresharomatics feed 400 can enter the process either via line 401 intoseparation zone 420 or via line 402 into the combined reaction zone 450.The aromatics recovered from separation zone 420 is introduced intocombined reaction zone 450 via line 403, and the fresh olefin feedenters the process via line 405 into the combined reaction zone 450. Thepolyalkylaromatic product recovered in separation zone 420 is introducedinto the combined reaction zone 450 via line 404. The effluent from thecombined reaction zone 450 is sent to separation zone 420 via line 406.The monoalkylated product is removed in the separation zone via line421.

[0053] As seen in FIG. 4, the second embodiment of the present inventioncomprises the following process steps:

[0054] (a) introducing into a combined reaction zone by three or moreindividual component feeds or one or more at least partly combinedfeeds, a reaction mixture comprising fresh and recycle aromatics, fresholefin, and recycled polyalkylaromatics, wherein the molar ratio ofaromatics to olefin in the mixture is in excess of 1:1, and the weightratio of aromatics to recycle polyalkylaromatics is in excess of 0.2:1,and also wherein the combined reaction zone includes a suitable catalystor catalyst mixture capable of catalyzing both alkylation andtransalkylation;

[0055] (b) contacting the reaction mixture with the catalyst(s) undersufficient reaction conditions to react essentially all the olefins inthe reaction mixture to monoalkylated aromatics and polyalkylatedaromatics, and to react the aromatics and the polyalkylaromatics in thereaction mixture to produce additional monoalkylaromatics, to produce aneffluent from the combined reaction zone comprising monoalkylatedaromatics, polyalkylated aromatics and the unreacted aromatics, furtherwherein the amount of polyalkylaromatics in the effluent is about thesame as that in the total feed to the reaction zone; and,

[0056] (c) introducing the reaction zone effluent into a separation zonewherein the desired monoalkylated aromatics product is isolated andrecovered and the unreacted aromatics and polyalkylated aromatics arerecovered and recycled.

[0057] The combined reaction step of this second embodiment of thepresent invention may be carried out in at least partial liquid phase attemperatures between about 150° F. (66° C.) and 900° F. (482° C.) and atpressures between about 150 (1034 kPAg) and 2000 psig (13788 kPAg), overone or more beds of suitable catalyst(s) comprising at least one solidacid oxide selected from the group consisting of: zeolite beta, zeoliteY, ZSM-5, PSH-3, ITQ-2, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58,MCM-68, faujasite, mordenite, porous crystalline magnesium silicates,and tungstate modified zirconia. The reaction of aromatics and olefin toproduce the monoalkylaromatics and polyalkyl-aromatics, and the reactionof aromatics and polyalkylaromatics to produce additionalmonoalkylaromatics, is believed to take place simultaneously over atleast one catalyst bed.

[0058] The combined reaction zone of this embodiment of the presentinvention can be housed in one or more vessels. Each reaction vessel maycomprise one or more catalyst beds of the same or different catalysts ormixtures of suitable catalysts. Olefin feed is introduced into at leastone of the catalyst beds, but not necessarily into each of the beds ifthere is more than one. Part of the total effluent from the combinedreaction zone may be recycled back to some or all of the catalyst beds,with or without cooling, for temperature control purposes.

[0059] One variation of this embodiment of the invention can have freshand recycle aromatics, effluent recycle, and recycle polyalkylaromatics(but not the olefin feed) introduced to the first of a plurality ofsequential catalyst beds. In such embodiment, olefin feed can then beintroduced into some or all of the downstream catalyst beds.

[0060] The overall molar ratio of aromatics to olefin fed to thereaction zone is in excess of 1:1, preferably between about 1:1 and20:1, more preferably about 2:1. The olefin fed to the reaction zone isessentially completely reacted. The overall weight ratio of aromatics topolyalkylaromatics fed to the alkylation zone in excess of 0.2:1,preferably is between about 0.2:1 and 20:1, more preferably about 2:1.

[0061] The following examples will further illustrate the practice andadvantages of the present invention.

EXAMPLE 1

[0062] For production of cumene, computer simulations were carried outto determine the required total benzene circulation at differentalkylator feed benzene to propylene molar ratios. The following fourreactor configurations were considered: (1) the conventional parallelalkylator and transalkylator reactor configuration (FIG. 1); (2) thetransalkylator-alkylator cascaded configuration provided in U.S. Pat.No. 5,902,917 (Collins) and U.S. Pat. No. 6,096,935 (Schulz) (FIG. 2);(3) the configuration of the first embodiment of thisinvention—alkylator and transalkylator in series configuration (FIG. 3);and, (4) the configuration of the second embodiment of thisinvention—combined alkylation/transalkylation zone (FIG. 4).

[0063] The weight ratio of benzene to polyisopropylbenzenes in thetransalkylator feed in the first two reactor configurations consideredabove was 2. As shown in FIG. 5, the two reactor configurations providedin the present invention require significantly less benzene circulationthan either the conventional parallel alkylator-transalkylatorconfiguration (parallel ALK and TRA—dotted line) or the cascadedtransalkylator-alkylator configuration (cascaded TRA-ALK—solid line),thereby confirming the superiority of the reactor embodiments of thisinvention (ALK-TRA in series configuration—dashed line) and (CombinedALK/TRA configuration—bold face dots).

EXAMPLE 2

[0064] An alkylation reactor and transalkylation reactor were configuredin a series configuration in accordance with FIG. 3 of the presentinvention. An MCM-22 type catalyst provided by ExxonMobil ChemicalCompany (identified as MC-1124) was loaded into the alkylation reactor.The amount of the catalyst loaded in the rector was 60 grams. A feedcomprising 30 grams per hour (0.71 moles/hr) of propylene and 110 gramsper hour (1.41 moles/hr) of benzene was introduced into the alkylationreactor. The alkylation reactor inlet temperature was maintained at 262°F. (128° C.). The alkylation reactor outlet temperature was maintainedat about 284° F. (140° C.) by recycling part of the alkylation reactoreffluent back to the inlet of the alkylation reactor. The alkylationreactor pressure was maintained at about 370 psig (2551 kPAg).

[0065] Another MCM-22 type catalyst provided by ExxonMobil ChemicalCompany (identified as MC-1122) was loaded into the transalkylationreactor. The amount of the catalyst loaded in the reactor was 15 grams.A feed comprising 17 grams per hour of alkylator effluent from the abovealkylation reactor and 4 grams per hour of diisopropylbenzenes recoveredfrom alkylator effluent was introduced into the transalkylation reactor.No fresh benzene was fed to the transalkylator zone.) Thetransalkylation reactor inlet temperature was maintained at 320° F.(160° C.), and the transalkylation reactor pressure was maintained atabout 370 psig (2551 kPAg). A comparison of diisopropylbenzenes in thealkylator effluent, the recovered diisopropylbenzenes, and thetransalkylator effluent, as listed in TABLE 1 below, shows thatsubstantially all of the diisopropylbenzene byproduct produced in thealkylator were reacted to monoalkylaromatic compound in thetransalkylator. TABLE 1 In alkylator In recovered In transalkylatorCompound effluent, g/hr DIPB, g/hr effluent g/hr Benzene 8.4 0.0 7.4Cumene 6.9 0.0 9.3 Diisopropylbenzenes 1.3 4.0 4.0

EXAMPLE 3

[0066] A combined alkylation-transalkylation reactor was configured inaccordance with FIG. 4 of the present invention. An MCM-22 type catalystprovided by ExxonMobil Chemical Company (identified as MC-1571) wasloaded into the combined reactor. The amount of the catalyst loaded inthe combined rector was 60 grams. A feed comprising 30 grams per hour ofpropylene (0.71 moles/hr), 101 grams per hour of benzene (1.29moles/hr), and 59 grams per hour of recycle diisopropylbenzenes wasintroduced into the combined reactor. The recycle diisopropyl-benzeneswas of about 93% purity. The combined reactor inlet temperature wasmaintained at 365° F. (171° C.). The combined reactor outlet temperaturewas maintained at 361° F. (183° C.) by recycling part of the combinedreactor effluent back to the combined reactor inlet. The combinedreactor pressure was maintained at about 370 psig (2551 kPAg). Acomparison of the combined reactor feed and effluent listed in TABLE 2below indicates that the combined reactor produced 78 grams per hour(0.65 moles/hr) of cumene without producing essentially any additionaldiisopropylbenzene byproduct in this experiment. TABLE 2 Compound Infeed, g/hr In effluent, g/hr Propylene 30 0 Benzene 101 51 Cumene 0 78Diisopropylbenzenes 55 55 Others 4 6

[0067] It will be apparent to those skilled in the art that otherchanges and modifications may be made in the above-described apparatusand processes for producing alkylaromatic compounds without departingfrom the scope of the invention herein, and it is intended that allmatter contained in the above description shall be interpreted in anillustrative and not a limiting sense.

We claim:
 1. A process for producing a monalkylated aromatic product ina reactor having an alkylation zone in series with a transalkylationzone, the process comprising the following steps: (a) introducing intothe alkylation zone by two or more individual component feeds or one ormore at least partly combined feeds, a reaction mixture comprising freshand recycle aromatics and fresh olefin, wherein the molar ratio ofaromatics to olefin in the mixture is in excess of 1:1, and also whereinthe alkylation zone includes a suitable alkylation catalyst(s); (b)contacting the aromatic/olefin mixture with the alkylation catalyst(s)under sufficient alkylation conditions to react essentially all theolefins in the mixture to monoalkylated aromatics and polyalkylatedaromatics, to produce an effluent from the alkylation zone comprisingmonoalkylated and polyalkylated aromatics and the unreacted aromatics;(c) introducing a feed into the transalkylation zone, the feedcomprising the effluent from the alkylation zone, recycledpolyalkylaromatics, and optionally additional aromatics, wherein thetransalkylation zone includes a suitable transalkylation catalyst; (d)contacting the feed to the transalkylation zone with the transalkylationcatalyst under sufficient transalkylation conditions to react at least apart of the aromatics and the polyalkylated aromatics in the feed toadditional monoalkylated aromatics to produce an effluent from thetransalkylation zone comprising the desired mono-alkylated aromatics andthe unreacted aromatics and polyalkylated aromatics; and, (e)introducing the transalkylation zone effluent into a separation zonewherein the desired monoalkylated aromatics product is isolated andrecovered and the unreacted aromatics and polyalkylated aromatics arerecovered and recycled.
 2. The process according to claim 1 wherein thealkylation reaction of step (b) is carried out in at least partialliquid phase at temperatures between about 150° F. (66° C.) and 900° F.(482° C.) and at pressures between about 150 psig (1034 kPag) and 2000psig (13788 kPag).
 3. The process of claim 1 wherein said alkylationcatalyst comprises at least one solid acid oxide selected from the groupconsisting of zeolite beta, zeolite Y, ZSM-5, PSH-3, ITQ-2, ZSM-12,MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, faujasite, mordenite,porous crystalline magnesium silicates, and tungstate modified zirconia.4. The process of claim 1 wherein overall molar ratio of aromatics toolefin fed to the alkylation zone is between about 1:1 to 20:1 such thatthe olefin fed to the alkylation zone is essentially completely reactedwith the aromatics feed.
 5. The process according to claim 1 wherein thetransalkylation reaction of step (d) is carried out in at least partialliquid phase at temperatures between about 150° F. (66° C.) and 900° F.(482° C.) and at pressures between about 150 psig (1034 kPag) and 2000psig (13788 KPag).
 6. The process according to claim 1 wherein thetransalkylation catalyst(s) comprises at least one solid acid oxideselected from the group consisting of: zeolite beta, zeolite Y, ZSM-5,PSH-3, ITQ-2, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68,faujasite, mordenite, porous crystalline magnesium silicates, andtungstate modified zirconia.
 7. The process according to claim 1 whereinthe overall weight ratio of aromatics to polyalkylaromatics fed to thetransalkylation zone is between about 0.2:1 and 20:1.
 8. A process forproducing a monalkylated aromatic product in a combined reactor zonecomprising the following process steps: (a) introducing into thecombined reaction zone by three or more individual component feeds orone or more at least partly combined feeds, a reaction mixturecomprising fresh and recycle aromatics, fresh olefin, and recycledpolyalkylaromatics, wherein the molar ratio of aromatics to olefin inthe mixture is in excess of 1:1, and the weight ratio of aromatics torecycle polyalkylaromatics is in excess of 0.2:1, and also wherein thecombined reaction zone includes a suitable catalyst or catalyst mixturecapable of catalyzing both alkylation and transalkylation; (b)contacting the reaction mixture with the catalyst(s) under sufficientreaction conditions to react essentially all the olefins in the reactionmixture to monoalkylated aromatics and polyalkylated aromatics, and toreact the aromatics and the polyalkylaromatics in the reaction mixtureto produce additional monoalkylaromatics, to produce an effluent fromthe combined reaction zone comprising monoalkylated aromatics,polyalkylated aromatics and the unreacted aromatics, further wherein theamount of polyalkylaromatics in the effluent is about the same as thatin the total feed to the reaction zone; and, (c) introducing thereaction zone effluent into a separation zone wherein the desiredmonoalkylated aromatics product is isolated and recovered and theunreacted aromatics and polyalkylated aromatics are recovered andrecycled.
 9. The process according to claim 8 wherein the reaction ofstep (b) is carried out in at least partial liquid phase at temperaturesbetween about 150° F. (66° C.) and 900° F. (482° C.) and at pressuresbetween about 150 psig (1034 kPag) and 2000 psig (13788 kPag).
 10. Theprocess according to claim 8 wherein the catalyst or catalyst mixturecomprises at least one solid acid oxide selected from the groupconsisting of zeolite beta, zeolite Y, ZSM-5, PSH-3, ITQ-2, ZSM-12,MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, faujasite, mordenite,porous crystalline magnesium silicates, tungstate modified zirconia andmixtures thereof.
 11. The process of claim 8 wherein overall molar ratioof aromatics to olefin fed to the reaction zone is between about 1:1 to20:1 and the aromatics to polyalkylaromatics fed to the reaction zone isbetween about 0.2:1 and 20:1 and such that the olefin fed to thereaction zone is essentially completed reacted with the aromatics feed.12. The process of claims 1-11 wherein the aromatics are benzene. 13.The process of claims 1-11 wherein the olefin are selected from thegroup consisting of ethylene and propylene.
 14. The process of claims1-11 wherein the monoalkylaromatics are selected from the group ofethylbenzene and cumene.
 15. The process of claims 1-11 wherein thepolyalkylaromatics are selected from polyethylbenzene andpolyisopropylbenzene.